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Tapping into Ambient light sensor and Dash Brightness knob

11K views 9 replies 3 participants last post by  DrivenDaily 
#1 ·
Does anyone know how to go about tapping into the ambient light sensor that is in the middle of our dash or the dash brightness knob?

I am trying to fashion a solution to the super bright mirror signal mod. I would like to be able to read the daylight sensor to decide if it is "day' or 'night' and then I would like to read the dash brightness knob to further adjust the brightness. I plan on using a microcontroller to control the side mirror flasher brightness via PWM.

I expect the daylight sensor and dash control knob to be variable resistors that provide a voltage to be read at the BCM. That would be the best case scenario as I could simply read that voltage with appropriate scaling via resistors to fit my 0-5V scale.

Has anyone checked out these signals? I haevn't gotten under the dash to have a look yet.

I believe I would be looking for DRLAMBIENT LIGHT SENS SIG as part of the BCM circuit 4 of 4 and I/P LAMPS DIMMER SW SIG also part of BMC circut 4 of 4 on the schematic that's been posted here before. Are these the correct signals?
 
#2 ·
It's way simpler than that! The parking lights being on or off can be your signal. If they're off let the LEDs be full brightness. If they're on then have the voltage dropped by a resistor. You can do this with an SPDT relay. Hook the parking lights up to the coil, the LEDs to common, resistor to NO, and the unaltered path (to either + or Gnd) to NC.

Thus, when the parking lights are off, the electrical path for the LEDs is through common to NC, mirroring the original path. When the parking lights are on, the coil is energized and the path for the LEDs is through common to NO through the dropping resistor.

I've been thinking about making this change myself but haven't gotten around to any mods yet this year.

For simplicity, of you use the Gnd leg of the circuit you can have both mirror LEDs use that path. Otherwise, if you use the + leg you'll have two resistors and either two SPDT relays or one DPDT.
 
#3 ·
Thanks Driven.

That is definitely a elegant solution to the blinding brightness. But alas, I had my heart set on being able to adjust the brightness with the interior dash knob as well. Does the instrument panel get dimmed in a simple fashion like that as well, with the knob being a potentiometer adjusting the voltage to the gauge lights?
 
#4 · (Edited)
#6 ·
Cool, I hope it's a POT. That would make things easy.

I forgot to ask you about your speaking backup system in your signature. What is that?
It has three sensors that can be attached permenently to the bumper or to "hinges" that you mount under the bumper. I mounted mine on the bumper. When the backup lights turn on the system is energized and it speaks distance measurements in English. It starts with "eight feet", then "five feet", "three feet", "two feet", "twelve inches", and "collision". It also detects if something crosses the path horizontally and won't stop sounding the alarm until you take it out of reverse.

I got it online. The brand is Poron, model is micro 3LV. Cost was a shade over $200 and it works perfectly! A friend in California had me install one each on his wife's Lincoln and his Ranger. They both loved them!

Install is easy but takes time to do it so that nothing is visible and all the wires are secured. Except for the sensors on the bumper nobody can see anything in my car. The processor module is mounted behind the carpet "door" for the fuse box in the trunk and the speaker is mounted just behind the left rear passenger's head restraint. Everyone in the car can hear it easily.

Using the schematics helps locate the proper wires. The rest is just labor.
 
#8 ·
Everyone that has been in my car seems to think it's a really cool item. You might need to carry a bat, then, when your buddies speak up and start to give you a hard time. Just tell 'em you're gonna adjust their attitude!
 
#10 ·
Ok, sounds like I have my to-do list for this weekend, huh? Hey, I'll even try to get the How-To for remote windows done as well.
 
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